CVE-2021-3939: Ubuntu-specific modifications to accountsservice (in patch file debian/patches/0010-set-language.patch) caused

Q: How do I fix CVE-2021-3939?

accountsservice: mitigate or apply the listed mitigation; ubuntu linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2021-3939 being exploited?

CVE-2021-3939 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-3939 affect?

CVE-2021-3939 affects accountsservice, ubuntu linux. Severity is high (CVSS 7.8). Ubuntu-specific modifications to accountsservice (in patch file debian/patches/0010-set-language.patch) caused the fallback_locale variable, pointing to static storage, to be freed, in the user_change_language_authorized_cb function. This i

Q: How urgent is CVE-2021-3939?

Priority 40/100. High severity; On your watchlist

This month

HIGH 7.8WATCHLISTMITIGATEMITIGATE

CVE-2021-3939 is a high-severity flaw (CVSS 7.8) affecting accountsservice, ubuntu linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Ubuntu-specific modifications to accountsservice (in patch file debian/patches/0010-set-language.patch) caused the fallback_locale variable, pointing to static storage, to be freed, in the user_change_language_authorized_cb function. This is reachable via the SetLanguage dbus function. This is fixed in versions 0.6.55-0ubuntu12~20.04.5, 0.6.55-0ubuntu13.3, 0.6.55-0ubuntu14.1.

Why this priority

High severity
On your watchlist

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	High
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.4% (top 69%)
CISA exploited list	No
Weakness	CWE-590, CWE-763
Published	2021-11-17
Last modified	2026-06-17

Publisher (CNA): Canonical Ltd. · Vendor: canonical

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-11-17 04:15 UTCPublished CVE record published
2026-06-17 04:06 UTCUpdated Record last modified

canonical accountsservice MITIGATE

Affected: >= 0.6.55-0ubuntu12\~20.04 and < 0.6.55-0ubuntu12\~20.05 · >= 0.6.55-0ubuntu13 and < 0.6.55-0ubuntu13.3 · >= 0.6.55-0ubuntu14 and < 0.6.55-0ubuntu14.1

Fixed in: 0.6.55-0ubuntu12\~20.05, 0.6.55-0ubuntu13.3, 0.6.55-0ubuntu14.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy accountsservice || rpm -q accountsservice || accountsservice --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

canonical ubuntu linux MITIGATE

Affected: 20.04 · 21.04 · 21.10

Fixed in: no fixed release known

Safe to downgrade to: a release before 20.04

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-3939?

accountsservice: mitigate or apply the listed mitigation; ubuntu linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-3939 being exploited?

CVE-2021-3939 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-3939 affect?

CVE-2021-3939 affects accountsservice, ubuntu linux. Severity is high (CVSS 7.8). Ubuntu-specific modifications to accountsservice (in patch file debian/patches/0010-set-language.patch) caused the fallback_locale variable, pointing to static storage, to be freed, in the user_change_language_authorized_cb function. This i

How urgent is CVE-2021-3939?

Priority 40/100. High severity; On your watchlist

Software pages

Ubuntu vulnerabilities · Debian vulnerabilities

Related CVEs

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CVE-2020-16127 LOW 2.8 UPGRADE An Ubuntu-specific modification to AccountsService in versions before 0.6.55-0ubuntu13.2, among other earlier
CVE-2020-16126 LOW 3.3 UPGRADE An Ubuntu-specific modification to AccountsService in versions before 0.6.55-0ubuntu13.2, among other earlier
CVE-2018-14036 MEDIUM 6.5 UPGRADE Directory Traversal with ../ sequences occurs in AccountsService before 0.6.50 because of an insufficient path

References

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